Traditional underground water distribution systems for residential and commercial areas often incorporate low flow or dead end portions by design. For instance, fire protection and land development codes often require oversized water mains for anticipated fire control and peak water demands. Such design features, although in the best interest of the community, have the effect of dramatically reducing water flow velocity and increasing water retention time within the water distribution system. The problem is further exacerbated by water distribution systems that experience large seasonal fluctuations in demand. These systems often experience additional reduction in water flow during non-seasonal periods of the year.
Low water flow conditions and corresponding increases in water retention time within portions of the water distribution system have the potential to degrade the chemical and microbiological quality of water transported through the distribution system. Degradation in water quality results from prolonged exposure to water system materials, internal sedimentation, and/or contaminant deposits within the piping system. Disinfectants are commonly used in an effort to control bacterial growth. However, as disinfectant residuals dissipate bacterial regrowth occurs.
The Federal Safe Drinking Water Act requires that potable, or drinkable, water systems maintain minimum disinfection residual levels, to prevent the regrowth of bacteria. In fact, mandatory testing programs have been enacted to track compliance and identify potential health hazards. Water systems failing to adhere to regulatory or operational water quality standards are subject to regulatory enforcement action, public disclosure of health hazards, and increased public and regulatory scrutiny.
Corrosion rates in low flow and stagnant areas can escalate as chemical reactions and microbiological activity increase. Corrosive water tends to dissolve certain materials commonly used in the construction of water distribution systems. The two primary metals of concern are iron and lead. Iron is commonly found in piping system materials. Lead is commonly found in older water systems that have incorporated lead joints, lead composite pipes and/or brass fittings. Elevated iron concentrations can result in violations of drinking water standards. In both potable and non-potable water distribution systems, excessive concentrations of iron can result in staining of structure surfaces, fixtures and clothing.
Bacterial hazards also abound in low flow or dead end portions of water distribution systems. Increased bacterial concentrations result from reductions in disinfection residuals which retard or prevent the regrowth of such bacteria. Maintenance of adequate water system disinfection residuals is necessary to afford protection from accidental or intentional introduction of microbiological contaminants into the distribution system. Microbiological films, referred to in the art as bio-films, can form on water distribution system components where adequate disinfectant residual levels are not maintained. Removal of such films is expensive and time consuming.
Historically, water distribution system compliance with water quality regulatory standards has been evaluated through the collection of water samples. Presently, samples are collected from private plumbing systems and stationary water sampling stations installed along the water system distribution system. These designated sampling locations often produce test results that are either inaccurate or not representative of water quality throughout the water distribution system.
Historically, the primary means of addressing water quality degradation in low flow or dead end areas has been to dispatch workers, on a complaint-by-complaint basis, to manually purge the water from a problem area of the system. This method does not provide an adequate solution, since its success is contingent on financial and human resource availability.
Another approach that has been employed to supplement manual flushing operations has been the use of increased concentrations of disinfectant residuals, in an attempt to counteract the effects of disinfectant residual dissipation, which is a time dependent function of chemical and biological reactions. Using this approach, the disinfectant residual level of the entire system is increased or, alternatively, disinfectant booster stations are positioned at strategic areas along the water distribution system. However, due to suspicions that chlorine and other water-disinfecting chemicals may be carcinogenic, or responsible for creating carcinogenic substances during the disinfection process, there is a general consensus that dosage rates must be minimized. For instance, the Federal Safe Drinking Water Act is expected to establish a maximum limit of 4 mg/l for chlorine.
The prior art does not provide an adequate solution for addressing the aforementioned water quality degradation problems common at low flow and dead end areas of water distribution systems. The need for an adequate solution has been heightened as a result of an increase in the occurrence of known and suspected carcinogens in water distribution systems. Further, manual purging of low quality water causes excessive amounts of water to be discharged from the system thus making operation impractical in areas of poor drainage and high pedestrian/vehicular traffic. Moreover, prior art systems are generally shut down in subfreezing temperatures to protect system components from the expansion of freezing water.
Accordingly, what is needed is an apparatus capable of analyzing water quality and purging low quality water from low flow or dead end areas of water distribution systems. Various configurations can be provided to make the system adaptable to address particular drainage and traffic conditions. In some cases, it would be desirable for the aforementioned apparatus to have an internal control system capable of automatically monitoring water quality and, subsequently, purging low-quality water from the low flow area based upon user defined water quality limits. In some cases, it would be further desirable for the analytical and purging functions of the apparatus to be controllable by a remotely operated device. Additionally, it would also be desirable, in some cases, for the apparatus to provide a system for permitting operation of the apparatus in subfreezing temperatures and a device for preventing contaminants from entering the water distribution system.